Valeria Giardino

In the present article, the current situation of the so-called philosophy of mathematical practice is discussed. First, its emergence is evaluated in relation to the “practical” turn in philosophy of science and in philosophy of mathematics. Second, the variety of approaches concerned with the practice of mathematics and the new topics being now object of research are introduced. Third, the possible replies to the question about what counts as mathematical practice are taken into account. Finally, some of the problems that are still open in the philosophy of mathematical practice are presented and some possible new directions of research considered.

An increasing number of studies have recently been devoted to the analysis of segments of the contemporary practice of mathematics. An important element of mathematical practice is proof, and proofs are often supplemented by diagrams and a specific terminology. Carter discusses a case in analysis in which some of the formal definitions arise from original proofs where diagrams were massively employed, irrespectively of the fact that they were then discarded from the final publication. In this paper, a case study of an article in which Feynman diagrams are indeed published as elements of a proof will be introduced. The main objective will be to try to unveil the complexities of what is accepted as a 'graphical argumentation' in an informal proof by pointing the attention towards what Connes and Kreimer defines as a 'toolkit' that is available to mathematicians, involving the familiarity with not only some form of intuition but also the appropriate context, in an interplay between different diagrammatic practices. This analysis will contribute to a wider discussion of the role of several kinds of diagrams in contemporary mathematics, going beyond geometry and across disciplines.

Is there anything like an experiment in mathematics? And if this is the case, what would distinguish a mathematical experiment from a mathematical thought experiment? In the present paper, a framework for the practice of mathematics will be put forward, which will consider mathematics as an experimenting activity and as a proving activity. The relationship between these two activities will be explored and more importantly a distinction between thought-experiments, real experiments, quasi experiments and proofs in pure mathematics will be provided. To do so, three examples of experimenting with triangles will be introduced and discussed.

In the first part of the article, a semiotic reading of the embodied approach to mathematics will be presented. From this perspective, the role of the sensorimotor in mathematics will be considered, by looking at some work in experimental psychology on the segmentation of formulas and at an analysis of the practice of topology as involving manipulative imagination. According to the proposed view, representations in mathematics are cognitive tools whose functioning depends on pre-existing cognitive abilities and specific training. In the second part of the paper, the view of cognitive tools as props in games of “make-believe” will be discussed; to better specify this claim, the notion of affordance will be explored in its possible extension from concrete objects to representations.

The aim of this article is to investigate specific aspects connected with visualization in the practice of a mathematical subfield: low-dimensional topology. Through a case study, it will be established that visualization can play an epistemic role. The background assumption is that the consideration of the actual practice of mathematics is relevant to address epistemological issues. It will be shown that in low-dimensional topology, justifications can be based on sequences of pictures. Three theses will be defended. First, the representations used in the practice are an integral part of the mathematical reasoning. As a matter of fact, they convey in a material form the relevant transitions and thus allow experts to draw inferential connections. Second, in low-dimensional topology, experts exploit a particular type of manipulative imagination which is connected to intuition of two- and three-dimensional space and motor agency. This imagination allows recognizing the transformations which connect different pictures in an argument. Third, the epistemic—and inferential—actions performed are permissible only within a specific practice: this form of reasoning is subject-matter dependent. Local criteria of validity are established to assure the soundness of representationally heterogeneous arguments in low-dimensional topology.

The objective of this chapter is to introduce some of the views that have been put forward in almost 20 years of research on diagrammatic proofs in the philosophy of mathematical practice. In Sect. 1, some contextual elements will be presented on the reasons why diagrammatic proofs have attracted so much philosophical attention in the past years. In Sect. 2, the “first wave” in the research on diagrammatic proofs based on the analysis of case studies will be described: this is how it started. In Sect. 3, the “second wave,” which is calling for “big pictures” and divides into two different strategies, will be discussed: this is where it is going. In Sect. 4, some conclusions will be drawn.

In this short Introduction to the present section, I will first briefly point out the reasons why the chapters collected here present original research in the context of the philosophy of the practice of mathematics, and open even newer perspectives. It is important to note that one crucial issue for future research will be to explore the connections within these chapters and with other chapters included in other sections – in particular, but not exclusively, the sections on Proof, on “Experimental” mathematics, and on the Semiology of Mathematical Practice. Second, I will present a short – and not exhaustive – summary of the themes that are tackled in the chapters. There will be overlaps and common threads: These chapters are indeed the final product of several discussions and exchanges within the community of the philosophers of the mathematical practice, which is extending toward other regions of philosophy thus blurring standard boundaries.

In the past 10 years, contemporary philosophy of mathematics has seen the development of a trend that conceives mathematics as first and foremost a human activity and in particular as a kind of practice. However, only recently the need for a general framework to account for the target of the so-called philosophy of mathematical practice has emerged. The purpose of the present article is to make progress towards the definition of a more precise general framework for the philosophy of mathematical practice by exploring two strategies. A first strategy is to turn to philosophy of mind and Edwin Hutchins' view of distributed cognition in order to better understand the cognitive issues at play when considering a community of mathematicians; a second strategy is to refer to philosophy of language and focus on Robert Brandom's inferentialism and mathematical conceptual content. A possible combination of these two views, called enhanced material inferentialism, is then put forward as a promising framework to account for the philosophy of mathematical practice.

Is there anything like an experiment in mathematics? And if this is the case, what would distinguish a mathematical experiment from a mathematical thought experiment? In the present paper, a framework for the practice of mathematics will be put forward, which will consider mathematics as an experimenting activity and as a proving activity. The relationship between these two activities will be explored and more importantly a distinction between thought-experiments, real experiments, quasi experiments and proofs in pure mathematics will be provided. To do so, three examples of experimenting with triangles will be introduced and discussed.

This introduction aims to familiarize readers with basic dimensions of variation among pictorial and diagrammatic representations, as we understand them, in order to serve as a backdrop to the articles in this volume. Instead of trying to canvas the vast range of representational kinds, we focus on a few important axes of difference, and a small handful of illustrative examples. We begin in Section 1 with background: the distinction between pictures and diagrams, the concept of systems of representation, and that of the properties of usage associated with signs. In Section 2 we illustrate these ideas with a case study of diagrammatic representation: the evolution from Euler diagrams to Venn diagrams. Section 3 is correspondingly devoted to pictorial representation, illustrated by the comparison between parallel and linear perspective drawing. We conclude with open questions, and then briefly summarize the articles to follow.

The objective of this article is to take into account the functioning of representational cognitive tools, and in particular of notations and visualizations in mathematics. In order to explain their functioning, formulas in algebra and logic and diagrams in topology will be presented as case studies and the notion of manipulative imagination as proposed in previous work will be discussed. To better characterize the analysis, the notions of material anchor and representational affordance will be introduced.

In the first part of the paper, previous work about embodied mathematics and the practice of topology will be presented. According to the proposed view, in order to become experts, topologists have to learn how to use manipulative imagination: representations are cognitive tools whose functioning depends from pre-existing cognitive abilities and from specific training. In the second part of the paper, the notion of imagination as “make-believe” is discussed to give an account of cognitive tools in mathematics as props; to better specify the claim, the notion of “affordance” is explored in its possible extension from concrete objects to representations.

It is possible to argue that the only ‘genuine’ experiments in mathematics are in fact thought experiments. Nevertheless, one preliminary question is to ask what genuine mathematica experiments are, and whether the activity of experimentation is a proper mathematical activity. In this article, I will consider which kind of conception of mathematics allows for the existence of experiments in mathematics and I will present the constraints these experiments are subject to. Then, I will discuss three examples to arrive at a general conclusion: experimentation is indeed a genuine mathematical activity, but its mechanisms are particular with respect to experimentation in the natural sciences.

In his book Gabriele Lolli discusses the notion of proof, which is, according to him, the most important and at the same time the least studied aspect of mathematics. According to Lolli, a theorem is a conditional sentence of the form ‘if T then A’ such that A is a logical consequence of T, where A is a sentence and T is a sentence or a conjunction or set of sentences. Verifying that A is a consequence of T generally involves considering infinitely many interpretations; so it is something which is impossible to do in finite terms. Proofs may serve as ‘shortcuts’ in this respect. A proof is defined by Lolli as any finite argument certifying that A is a consequence of T. A proof is a shortcut in the sense that it spares us considering infinitely many interpretations.The reason for such a very general definition of proof is Lolli's strong belief that mathematics is not a rigid system of explicit rules, but rather a set of tools; as a consequence, there is no prescription as to what a proof should or should not be. Actually, mathematics is historically situated and not timeless, and the history of mathematics is the …

The aim of this article is to explain why knot diagrams are an effective notation in topology. Their cognitive features and epistemic roles will be assessed. First, it will be argued that different interpretations of a figure give rise to different diagrams and as a consequence various levels of representation for knots will be identified. Second, it will be shown that knot diagrams are dynamic by pointing at the moves which are commonly applied to them. For this reason, experts must develop a specific form of enhanced manipulative imagination, in order to draw inferences from knot diagrams by performing epistemic actions. Moreover, it will be argued that knot diagrams not only can promote discovery, but also provide evidence. This case study is an experimentation ground to evaluate the role of space and action in making inferences by reasoning diagrammatically.

Poiché i miei interessi di ricerca si concentrano sul rapporto tra spazio e rappresentazione, nel presente articolo commenterò un lavoro di Achille C. Varzi pubblicato nel 2008 e intitolato, nella sua versione italiana, «Configurazioni, regole e inferenze». Accennerò anche a un secondo articolo scritto da Varzi e Massimo Warglien e pubblicato nel 2003, intitolato «The Geometry of Negation». Mi rivolgerò poi alla psicologia sperimentale, collegando alcuni aspetti delle osservazioni di Varzi a un articolo di Johnson- Laird del 2005 intitolato «The Shape of Problems». Nelle conclusioni, farò un ultimo riferimento a un articolo di Varzi pubblicato nel 2000, scritto con Philip Kitcher e intitolato «Some Pictures Are Worth 2 אo Sentences». Le parole configurazioni, geometry, shape e picture nei titoli degli articoli di cui mi occuperò sono dei buoni indizi per capire quale sia il filo rosso che lega a mio avviso tutti questi lavori.

The objective of this article is twofold. First, a methodological issue is addressed. It is pointed out that even if philosophers of mathematics have been recently more and more concerned with the practice of mathematics, there is still a need for a sharp definition of what the targets of a philosophy of mathematical practice should be. Three possible objects of inquiry are put forward: (1) the collective dimension of the practice of mathematics; (2) the cognitives capacities requested to the practitioners; and (3) the specific forms of representation and notation shared and selected by the practitioners. Moreover, it is claimed that a broadening of the notion of ‘permissible action’ as introduced by Larvor (2012) with respect to mathematical arguments, allows for a consideration of all these three elements simultaneously. Second, a case from topology – the proof of Alexander’s theorem – is presented to illustrate a concrete analysis of a mathematical practice and to exemplify the proposed method. It is discussed that the attention to the three elements of the practice identified above brings to the emergence of philosophically relevant features in the practice of topology: the need for a revision in the definition of criteria of validity, the interest in tracking the operations that are performed on the notation, and the constant and fruitful back-and-forth from one representation to another in dealing with mathematical content. Finally, some suggestions for further research are given in the conclusions.

In this article, I will discuss the relationship between mathematical intuition and mathematical visualization. I will argue that in order to investigate this relationship, it is necessary to consider mathematical activity as a complex phenomenon, which involves many different cognitive resources. I will focus on two kinds of danger in recurring to visualization and I will show that they are not a good reason to conclude that visualization is not reliable, if we consider its use in mathematical practice. Then, I will give an example of mathematical reasoning with a figure, and show that both visualization and intuition are involved. I claim that mathematical intuition depends on background knowledge and expertise, and that it allows to see the generality of the conclusions obtained by means of visualization.